Hydraulic control valves



June l, 1965 R. G. PEACH HYDRAULIC coNTRoL vALvEs Filed March 12, 1962 United States Patent O This invention relates to hydraulic control valves and more particularly to hydraulic control valves of the spool type.

Systems heretofore known in which a iluid flow is supplied through a hydraulic control valve have usually -suiered from the disadvantages that in cases where the full iixed flow rate supplied is greater than the requirements, the supply has to be effected via additional ow n regulating valves outside the control valve or via a control sp'ool having a restricted waist ior holes, and such systems are not only complicated to construct and install but systems using a control spool with a restricted waist or holes are wasteful to operate on account of the unnecessary pressure to which the iluid must be raised.

The present invention has for its main objective to overcome these disadvantages and the invention accordingly consists in a hydraulic control valve comprising a Valve body having a bore therethrough, at least one service portV and a high and a low pressure port in communication with said bore, a control spool having a passage therethrough slidably engaged in said bore and provided with service control ports therein at one end and constructed and arranged so that in one position of said spool, communication is established between the service port and the low pressure port through said passage and is precluded between the high pressure port and said passage, and in another position thereof communication is established between the service port and the highpressure port through said passage and is precluded between the low pressure port and the passage, said spool having by-pass port means establishing communication between said low pressure port and sai-d passage and spaced from said end having the service control ports therein, a valve seat in said passage between said service control ports and said by-pass port means, an elongated by-pass valve member in said passage adapted to co-operate with said seat and constructed and arranged so that a predetermined flow rate is maintained from said high pressure port through said passage to said service port when said spool is in said another position, means biasing said valve member to a closed position on said seat, said-'valve being pressure balanced at its opposite ends and responsive to pressure from sai-d high pressure port when said spool is in said another position to move from said seat against the force of the biasing means, whereby pressure in excess of a predetermined amount is by-passed to said by-pass port. n

The invention also consists in a hydraulic control valve comprising a valve body having a bore therethrough, at least one service port and a high and ailow pressure port in communication with `said bore, a control spool having a passage therethrough slidably engaged in said bore and provided with service control ports Itherein at one end and constructed and arranged so that in one position of said spool, communication is established Vbetween the service port and the low pressure port through said passage and is precluded between the high pressure port and said passage, and in another position thereof communication is established between the service port and the high pressure port through said pas-sage and is precluded between the low pressure port and the passage, said spool having by-pass port means establishing communication 3,l86,424 Patented June 1, 1965 ice between said low pressure port and said passage and spaced from said end having the service control ports therein, dual valve seats in said passage between said service control ports and said by-pass port means, dual elongated by-pass valve members in said passage adapted to co-operate with said seats and constructed and arranged so that a predetermined flow rate is 4maintained from said high pressure port through said passage to said service port when said spool is in said another position, means biasing said valve members to a closed position on said seats, said valve being pressure balanced at its `opposite ends and responsive to pressure from said high pressure port when said spool is in said another position to move fromsaid seat against the force of the biasing means, whereby pressure in excess of a predetermined amount is by-passed to said by-pass port.

The invention will be more completely understood from the following detailed description which is given in conjunction with the accompanying drawing which shows a sectional side View of a spool type hydraulic control valve constructed in accordance with the invention.

Referring now to this drawing 1 is the main casing in the bore of which the control spool 2 of an open centre parallel circuit hydraulic control valve is slidably mounted, this spool being provided with two ilow control valves 3, 3', one for each service. With the main control spool 2 in the neutral position, the fluid supply is passed to the low pressure return gallery 5 of the valve via the central waist 6 of the main control spool. Movement of the control spool 2 in either direction will then shut oit the escape of oil via the waist 6 of the main control spool and will raise the pressure in the galleries 7 and 8. If the main control spool is now moved in to the housing, that is to say, from left to right in the drawing, one service control port 10 will be connected to the highpressure gallery 7 and the other service port 9 to the low pressure gallery 5. If however, the plunger and control spool are moved in the opposite direction, the second service port 9 will be connected to the high pressure gallery 8 and the rst service port 10 will be connected to the low pressure gallery Si. The flow control Valves 3 and 3 for the two services take the form of elongated by-pass valve members comprising flow control plungers whichrare slidably disposed in the bore of the spool 2. Each of these plungers is arranged to seat against a tubular stop 11 which seats in an internal seat 12 cut into the spool at one end, and is guided by a sleeve 13 located inthe spool at the other end, and the plunger is urged towards the stop 11 by a helical spring 14 mounted between the sleeve 13, and a shoulder 15 on the plunger, a central passage 16 being formed through the plunger to balance pressure between the ends. For any particular direction of movement, the flow control plunger associated with the service port 9 or 10 to be connected with a high pressuregallery 7 or 8 will be supplied with fluid through the high pressure spool port 17 to the space 18. The ilow then passes from this space via an annular clearance 19 or through slots in the plunger land to the space 20, whence it escapes via the low pressure spool port 22 to the service port 9 or 10. The passage of fluid via the clearance space 19 causes a pressure drop across the plunger land thus providing a force to compress the return spring 14. This allows part of the ilow to by-pass at the internal seat of the valve andthe by-pass flow makes its exit into the low pressure gallery 5 via the ports 21.

An alteration of the service condition such as would tend to allow the ilOw to increase will cause a greater pressure drop .to occur through the clearance 19 and this would result in a greater compression of the return spring 14. This in turn will allow a greater area to be opened to the by-pass ilow and the controlled flow will consequently be reduced. Conversely a condition tending to reduce the now from the service port will reduce the pressure drop through the clearance i9 thus allowing the spring to extend further so as to shut oft the by-pass ilow area and increase the controlled flow. The flow control valve is therefore self-regulating and pressure compensating. Y

The provision of by-pass flow regulators of the type hereinbefore described does not impair the inching characteristics of the control spool. As the neutral circulation galleries are cut off in favour of the supply to the high pressure galleries 7 and S, the ports 17 and 22 are e opened progressively thus allowing the ilow to increase up to the flow setting of the regulator before the by-pass area at the seat end of the flow regulator unit begins to open. Consequently, the ini-tial control is effected by means of throttling on the control spool ports.

When one end of the control spool 2 is -selected to supply a service port, the other end selects the connection of the other service port to the low pressure gallery 5. Under this condition luid from one service port 10 enters the spool holes ll'7 into the space 1S and the flow passes from the space 18 via the clearance 19, -space 20, and holes 22 into the low pressure gallery 5. The flow control valve operates as before, passing a controlled por- Vtion of the flow to the low pressure gallery'via the holes 22 in the spool, and passing the surplus flow via the seat opening at the other end of the flow control plunger. Under this condition the correct proportion of the ow is normally a matter of indilierence.

It is to be understood that the control spool shown may be one of a number of such spools containing flow regulating valves, all of which may be mounted in the common casing l, so as to communi-cate with common sources of high and low pressure, the spools being conveniently disposed parallel to one another, and arranged in a manner similar to that shown in the drawing.

I claim:

l. Hydraulic control valve comprising a valve body having a bore therethrough, at least one service port and a high and a low pressure port in communication with said bore, a control spool having a passage therethrough slidably engaged in said bore and provided with service control ports therein at one end and constructed and arranged so that one position of said spool, communication is established between the service port and the low pressure port through said passage and is precluded between the high pressure port and said passage, and in another position thereof communication is established between the service port and the high pressure port through said passage and is precluded between the low pressure port and the passage, said spool having by-pass port means establishing communication between said low pressure port and said passage and spaced from said end having the service control ports therein, a valve seat in said passage between said service control ports and said by-pass port means, an elongated by-pass valve member in said passage adapted to co-operate with said seat and constructed and arranged so that a predetermined flow rate is maintained from said high pressure port through said passage to said service port when said spool is in said another position, means biasing said valve member to a closed position on said seat, said valve being pressure balanced at its opposite ends and responsive to pressure from said high pressure port when said spool is in said another position to move from said seat against the force of the biasing means, whereby pressure in excess of a predetermined amount is by-passed to said by-pass port.

2. A hydraulic control valve comprising a valve body having a bore therethrough, at least one service port and a high and a low pressure port in communication with said bore, a control spool having a passage therethrough slidably engaged in said bore and provided with service control ports therein at one end and constructed and arranged so that in one position of said spool, communication is established between the service port and the low pressure port through said passage and is precluded between the high pressure port and said passage, and in another position thereof communication is established between the service port and the high pressure port through said passage and is precluded between the low pressure port and the passage, said spool having by-pass port means establishing communication between said low pressure port and said passage and spaced from said end having the service control ports therein, dual valve seats in said passage between said service control ports and said by-pass port means, dual elongated by-pass valve members in said passage adapted to oo-operate with said seats and constructed and arranged so that a predetermined llow rate is maintained from said high pressure port through said passage to said service port when said spool is in said another position, means biasing said valve members to a closed position on said seats, said valve being pressure balanced at its opposite ends and responsive to pressure from said high pressure port when said spool is in said another position to move from sai-d seat against the force of the biasing means, whereby pressure in excess of a predetermined amount is by-passed to said by-pass port.

3. Hydraulic control valve as claimed in claim 2, wherein each of said by-pass ow regulators comprises an auxiliary plunger slidably arranged within the passage of said control spool, each of ysaid auxiliary plungers being guided at the other end of said passage by a sleeve located within said control spool.

4. Hydraulic control valve as claimed in claim 3, and comprising spring means for urging each of said plungers towards said seat, said spring means comprising a helical spring surrounding the plunger body and being compressed between a circumferential shoulder on said plunger and a tubular stop formedin the bore of said control spool.

5. Hydraulic control valve as claimed in claim 3, wherein each of said plungers has a centrally disposed hole extending longitudinally therethrough for ensuring pressure balance between the ends of the plungers.

6. Hydraulic control valve as claimed in claim 4, and comprising an annular restricted clearance space between said shoulder and the internal Wall of said control spool for accommodating the controlled flow of fluid, and whereby a pressure loss is caused, thus energising the ilow control plungers.

7. Hydraulic contr-ol valve as claimed in claim 4, wherein each said plunger has at least one slot or passage in its land for accommodating the control flow fluid, and whereby a pressure loss is caused, thus energising the flow control plungers.

ISADOR WEEL, Primary Examiner.

WILLIAM F. ODEA, Examiner. 

1. HYDRAULIC CONTROL VALVE COMPRISING A VALVE BODY HAVING A BORE THERETHROUGH, AT LEAST ONE SERVICE PORT AND A HIGH AND A LOW PRESSURE PORT IN COMMUNICATION WITH SAID BORE, A CONTROL SPOOL HAVING A PASSAGE THERETHROUGH SLIDABLY ENGAGED IN SAID BORE AND PROVIDED WITH SERVICE CONTROL PORTS THEREIN AT ONE END AND CONSTRUCTED AND ARRANGED SO THAT ONE POSITION OF SAID SPOOL, COMMUNICATION IS ESTABLISHED BETWEEN THE SERVICE PORT AND THE LOW PRESSURE PORT THROUGH SAID PASSAGE AND IS PRECLUDED BETWEEN THE HIGH PRESSURE PORT AND SAID PASSAGE, AND IN ANOTHER POSITION THEREOF COMMUNICATION IS ESTABLISHED BETWEEN THE SERVICE PORT AND THE HIGH PRESSURE PORT THROUGH SAID PASSAGE AND IS PRECLUDED BETWEEN THE LOW PRESSURE PORT AND THE PASSAGE, SAID SPOOL HAVING BY-PASS PORT MEANS ESTABLISHING COMMUNICATION BETWEEN SAID LOW PRESSURE PORT AND SAID PASSAGE AND SPACED FROM SAID END HAVING THE SERVICE CONTROL PORTS THEREIN A VALVE SEAT IN SAID PASSAGE BETWEEN SAID SERVICE CONTROL PORTS AND SAID BY-PASS PORT MEANS, AN ELONGATED BY-PASS VALVE MEMBER IN SAID PASSAGE ADAPTED TO CO-OPERATE WITH SAID SEAT AND CONSTRUCTED AND ARRANGED SO THAT A PREDETERMINED FLOW RATE IS MAINTAINED FROM SAID HIGH PRESSURE PORT THROUGH SAID PASSAGE TO SAID SERVICE PORT WHEN SAID SPOOL IS IN SAID ANOTHER POSITION MEANS BIASING SAID VALVE MEMBER TO A CLOSED POSITION ON SAID SEAT, SAID VALVE BEING PRESSURE BALANCED AT ITS OPPOSITE ENDS AND RESPONSIVE TO PRESSURE FROM SAID HIGH PRESSURE PORT WHEN SAID SPOOL IS IN SAID ANOTHER POSITION TO MOVE FROM SAID SEAT AGAINST THE FORCE OF THE BIASING MEANS, WHEREBY PRESSURE IN EXCESS OF A PREDETERMINED AMOUNT IS BY-PASSED TO SAID BY-PASS PORT. 